The electrokinetic potential of a microchannel is measured as a function of MgSO4 concentration and
pH. At low MgSO4 concentration, the electrokinetic potential varies as a function of pH, becoming
positive at low pH and negative at high pH. At low pH, addition of large amounts of MgSO4 causes
the electrokinetic potential to decrease in magnitude, although it stays positive. At high pH, addition
of large amounts of MgSO4 causes the electrokinetic potential to change signs and become positive.
Of the four ions (H+, OH-, Mg+2, SO4-2), which are potential-determining? Which are indifferent?
Which are specifically adsorbing?